Abstract
A series of thirty-five engraved gems from the collection of the Museum fur Kunst und Gewerbe, Hamburg, were re-examined using non-destructive material-science methods in order to verify the previously determined rock type. The results of four selected, engraved gems containing pictorial elements as well as inscribed letters are presented in detail as a showcase of opaque gems. These intaglios originate from different epochs and places in the Mediterranean. They were analysed using both classical gemmological approaches and the more advanced Raman and infrared-reflectance spectroscopic methods, which can fingerprint the solid material on the basis of its atomic structure and chemical composition. The results demonstrate the potential of these spectroscopic methods for unambiguous identification of engraved gems and, more importantly, the necessity of applying them along with traditional gemmological methods for a correct material identification, which may furthermore help in tracing the origin of the inscribed gem.
